He shows up for three verses in B'reshit [Genesis] 14 and then all but vanishes, yet the whole priesthood of the Messiah hangs on him. Malki-Tzedek is priest and king at once, and king of Salem, which is Jerusalem. No genealogy, no Levitical line, older than Levi himself.

Tehillim [Psalms] 110:4 swears that the coming King will be a priest forever after the order of Malki-Tzedek, and Hebrews 5 through 7 names that priest as Yeshua. Priest and king in one person, tied to Jerusalem from the start, is exactly how the One who returns is dressed at the end. The thread runs the length of the book.